1. Field of the Invention
The present invention relates to an ultrasonic welding device for welding films and in particular for welding longitudinal and/or transverse seams of bag packages, as well as to a packaging machine having such an ultrasonic welding device.
2. Description of the Prior Art
From the prior art, ultrasonic welding devices are known, particularly for welding plastic films. The ultrasonic welding devices typically include an ultrasonic sonotrode and an anvil, and a working gap is formed between the ultrasonic sonotrode and the anvil and the films to be welded are passed through it. A constant working gap between the ultrasonic sonotrode and the anvil is decisive for the quality of the welded seam. Because of the heat produced for instance in processing, the dimensions of the components can vary, which can have effects on the width of the working gap. An overly narrow working gap, however, typically worsens the material processing and can lead to damage to the films to be welded and the anvil. If the gap is too wide, an unacceptable weld seam quality is the result. From German Patent DE 195 26 354 C1, an ultrasonic welding device is known which has a sensor for determining a working gap width. A sonotrode is fastened in a mount, and the mount can be adjusted relative to the anvil via a separate adjusting device. However, this known device is very complex in its construction and expensive to produce. Moreover, this device requires a large amount of space, so that its use in packaging machines in particular necessitates a large amount of installation space for the machine.